The present invention relates to warning signal devices for respirators having pressurized gas supplies.
The utilization time of respirators with a pressure gas supply is determined and, above all limited, by the gas reserve present in the pressure gas tanks, such as the gas bottles. These respirators, therefore, have alarm devices which warn the user of the respirator, in good time, when the gas reserve falls below a certain quantity. Operation of the alarm device occurs with utilization of the operating pressure of the gas. It must then be ascertained, however, that the alarm device fulfills its function at all times, regardless of handling, when the respirator is put into operation.
A known warning signal device for respirators with a pressure gas supply has, in front of the signal device, which is operated by the pressure gas, a pressure-controlled first valve which, in the line leading to the signal device, a pressure controlled second valve is arranged. The control means of the second valve is pressurized on one side by the pressure in the line leading to the signal device, while the other side defines a space closed on all sides which communicates with this line through a throttle.
After the opening of the first valve, after the pressure on the pressure gas supply has dropped, the pressure gas can flow directly to the signal device and set it into operation. The second valve closes after a time determined by the throttle, thereby, interrupting the inflow to the signal device. The alarm is thus ended automatically. After complete consumption of the pressure gas supply and, hence, dropping of the pressure, the valves of the warning signal device return to their starting position, i.e., both valves are open.
At normal initiation into operation of the respirator, after the opening of the shut-off valve of the pressure gas tank, a rapid pressure buildup occurs within the warning signal device. This closes the first valve. The quantity of gas flow up to this moment is insufficient for a closing of the second valve, but briefly sets the signal device in operation. This is taken as a control sign for operational readiness of the warning signal device. If the opening of the shut-off valve during the initiation of operation is defectively slow, the pressure buildup in the warning signal device is retarded. A longer time will then pass before the first valve closes.
During this time the second valve then also closes and remains closed, because with the first valve closed, the pressure in the control space of the second valve is maintained and cannot be relieved through the throttle. In this case, therefore, no alarm occurs as the pressure decreases in the pressure gas supply. (See German patent specification No. 21 29 529).